Focal seizures are induced by the injection of penicillin into the hand-face area of the right motor cortex of the macaca mulatta at successive age levels from birth to young adulthood. The evolving seizure pattern in the developing brain is recorded by electrocorticography, electromyography, and clinical observations. The anatomical substrate, at selected age levels, is studied with particular interest in cortical organization, and in cortico-thalamic circuitry. These investigations are completed and the results published in scientific literature.